The present invention relates to generation of pulses. In particular, the present invention is a gated pulse generator with minimum gating interval discrimination.
In recent years, considerable effort has been expended in the development of solid state electronic traffic controllers to replace the prior art electro-mechanical traffic controllers. The solid state controllers have the advantages of lower cost, smaller size, lower power consumption, and greater flexibility in functions performed than the prior art devices.
In the programmable solid state traffic controller described in the above-mentioned co-pending patent application, there is a need for a device which will produce output pulses to sequence the traffic signals at an intersection in response to an input signal. For the purpose of this discussion, the input signal has two states which will be designated logic "1" and logic "0". These designations are arbitrarily assigned and may be reversed without changing the operation of the system.
The gated pulse generator must meet several requirements. First, it must generate an output pulse if the input signal is "0" for greater than a certain time period (usually about 2 microseconds). The gated pulse generator must continue to generate pulses if the input signal stays at "0" for a longer period. In other words, the gated pulse generator must emit an output pulse for every period in which the input signal is continuously "0" for greater than 2 microseconds.
Second, if the input signal changes from "0" to "1" before the 2 microsecond period has elapsed, no output pulse must be produced. The pulse generation cycle is terminated without a pulse being produced. The gated pulse generator, therefore, has a minimum gating interval discrimination. This eliminates noise transients which may be present in the input signal.
Third, once an output pulse is started, it must continue for its full duration no matter what happens to the input signal. In other words, the gated pulse generator is insensitive to the state of the input signal once the output pulse begins.